How the Hum Works

It starts every night around 10 p.m., just when you're about to fall asleep. The sound is hard to describe, a persistent low rumble like an 18-wheeler idling outside your window. But when you pull the curtain, there's nothing there.

Your wife thinks you're crazy — she and the neighbors don't hear a thing — and the doctor has ruled out tinnitus. But here you are, night after sleepless night, stuffing wads of tissue in your ears to block out the maddening sound. The more you try to ignore it, the louder it seems to get. Maybe you really are going crazy. Or maybe that's just what "they" want you to think!

All around the world — in locations as far-flung as an Australian beach town, an English country village and a desert outpost in New Mexico — thousands of people are being terrorized by a mysterious incessant noise known as the Hum.

Hum sufferers describe a low-frequency buzz accompanied by a rumbling vibration. It's worst at night, making it almost impossible to sleep. Other symptoms include debilitating headaches, nausea, nosebleeds and diarrhea. In one tragic case in England, the Hum drove a person to suicide [source: Alexander].

The Hum has baffled researchers since the 1970s, when the first widespread reports of the unexplained acoustic phenomenon cropped up in rural England. Armed with highly sensitive instruments, teams of scientists have attempted to hunt down the source of the unrelenting noise. The results? Inconclusive.

Theories abound to explain the origins of the Hum, from the plausible — power lines, cell phone towers and industrial fans — to the more, uh, imaginative. Conspiracy theorists have exposed the Hum as the work of the CIA, the military, and of course, aliens.

So what exactly is this mystifying noise, unheard by most, but an absolute torture to some? Does the Hum have an environmental origin or is it, in fact, all in their heads?

We'll start our investigation by exploring some Hum hotspots around the globe and figuring out what the strange phenomena have in common.